[Feature Request] SAGAs

[lorensr]

SAGA: https://microservices.io/patterns/data/saga.html

Current state

We have SAGA helpers in:

• Java (Basic—it's just cleanup code. Mostly users implement their own classes.)
• PHP
• coinbase-ruby

Discussion excerpts

• One benefit of having Saga in Java SDK that people see it as a "feature" of the platform. We know that it is implementable from scratch in a few hours. But new users look for a "checkbox" to check.
• It is one of the core use cases we want to support natively
• My only argument that we should actually design Sagas and improve this class functionally. We need to make some better wrapper around this whole Subtransactions Implemented As Child Workflow Waiting For Signal (which is more of two-factor-commit than a saga). We don’t even have it written right now as our advice how to implement SAGAs. We need a better and safer abstraction.
• It requires PM/Design work. So I would say SAGA looks like a stream of work to me.
• It needs a careful design aligned with our best practices that we usually recommend to people. Decomposition into typical scenarios, understanding what kind of tooling will be covering them best in the most flexible way.
• There are two pretty distinct scenarios for Saga: synchronous and asynchronous (which is not time bound). I think we should think hard how to make Sagas work efficiently in the synchronous scenario. This might require significant server side changes. But the payout can be pretty significant as can take on a lot of transactional use cases.

Related

• TS issue: [Feature Request] Add SAGA helpers? sdk-typescript#456

cc @mnichols

[bergundy]

We pretty much decided we don’t want this in the sdks

[bergundy]

I’d be open to seeing a more concrete proposal, worth thinking about.

[cretz]

Same. @Spikhalskiy has mentioned that even the rudimentary Saga implementation in Java does not have the full, proper feature set.

The three existing implementations are so simple, anyone can just collect activities and run them in parallel and/or cleanup when they are done and/or continue on error. Having a utility called "Saga" that is just a loop seems a bit silly, but if it was a more full-featured implementation it may make sense.